Method and server for providing notary service for file and verifying file recorded by notary service

ABSTRACT

A method is provided for providing a notary service for a file, the method including the steps in which: (a) when a notary service request for a specific file is obtained, a server generates, by using a hash function, or supports the generation of, a message digest of the specific file; and (b) if a predetermined condition is satisfied, the server registers, in a database, or supports the registration of, a representative hash value or a value obtained by processing the representative hash value, the representative hash value being generated by calculating at least one neighboring hash value that matches a specific hash value, wherein the specific hash value is a hash value of the result of encrypting the message digest with a private key of a specific user and a private key of the server.

FIELD OF THE INVENTION

The present invention relates to a method for providing a notary servicefor a file and verifying the file recorded by the notary service; andmore particularly, to the method for providing the notary service forthe file and verifying the file recorded by using the notary service,including a “notary process” of, if a notary service request for thefile is acquired, generating or supporting another device to generate aspecific message digest of the file by using a hash function, and, ifone of anchoring conditions is satisfied, registering or supportinganother device to register a first representative hash value or itsprocessed value in a database, wherein the representative hash value isgenerated by using a specific hash value and its corresponding at leastone neighboring hash value, and wherein the specific hash value is ahash value of a result acquired by encoding the specific message digestwith a private key of a specific user and a private key of a server, anda “verification process” of, if a verification request for the file isacquired, and if a second representative hash value or its processedvalue, generated by using input data included in the verificationrequest, corresponds to the first representative hash value or itsprocessed value registered in the database, determining or supportinganother device to determine that verification of the file is completed,and the server using the same.

BACKGROUND OF THE INVENTION

Authentication is an act of publicly certifying the existence or thecontents of a specific fact or specific legal relations. When theauthentication of the specific legal relations is requested, anauthentication officer generally writes, signs and seals, and stores adocument in an authentication office.

However, there are constraints of time and space, and a possibility ofmissing, forging, and falsifying an authenticated document in aconventional authentication method because a client physically visitsthe authentication office with a document to be authenticated and itscertificate is stored in the authentication office.

Herein, the inventor of the present invention developed anauthentication system for a file to perform the authentication inreal-time without a possibility of forgery and falsification and withoutconstraints of space by recording authentication information in ablockchain of virtual currency and filed a patent application, KoreanPatent Application No. 2015-0188978.

However, there are disadvantages such as a bottleneck in providing theservice caused by the increased number of transactions since theauthentication system for the file using the blockchain generates an OPmessage for every file and records it in the blockchain, and high costsfor a service management because the transaction fee must be paid everytime.

Accordingly, there is a need for a technical solution that cancompensate for the disadvantages, thereby guaranteeing a fast serviceand reducing the costs while taking the advantage of the authenticationsystem for the file to perform the authentication in real-time withoutthe possibility of forgery and falsification and without constraints ofspace.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve all the aforementionedproblems.

It is another object of the present invention to guarantee fast servicespeed and reduce a transaction cost, when providing a notary service fora file to perform authentication and verification in real-time byrecording authentication information in a blockchain of virtualcurrency.

It is still another object of the present invention to improve servicespeed and reduce the transaction cost, by configuring a Merkle treeusing information on the notary service and registering only a rootvalue of the Merkle tree in the blockchain instead of registering all ofthe information on the notary service in the blockchain.

It is still yet another object of the present invention to provideguaranteed integrity of a database by performing the verification usingthe Merkle tree generated in response to a verification request for thefile.

In accordance with one aspect of the present invention, there isprovided a method for providing a notary service for a file, includingsteps of: (a) a server, if a notary service request for the file isacquired, generating or supporting another device to generate a specificmessage digest of the file by using a hash function; and (b) the server,if one of anchoring conditions is satisfied, registering or supportinganother device to register a representative hash value or its processedvalue in a database, wherein the representative hash value is generatedby using a specific hash value and its corresponding at least oneneighboring hash value, and wherein the specific hash value is a hashvalue of a result acquired by encoding the specific message digest witha private key of a specific user and a private key of the server.

In accordance with another aspect of the present invention, there isprovided a method for verifying a file recorded by using a notaryservice, including steps of: (a) a server acquiring or supportinganother device to acquire a verification request for the file, oncondition that the server has acquired a notary service request for thefile, and then has registered a first representative hash value or itsprocessed value in a database, wherein the first representative hashvalue is generated by using a first specific hash value and itscorresponding at least one neighboring hash value under one of anchoringconditions, and wherein the first specific hash value is a hash value ofa result acquired by encoding a specific message digest of the file witha private key of a specific user and a private key of the server; and(b) the server, if a second representative hash value or its processedvalue, generated by using input data included in the verificationrequest, corresponds to the first representative hash value or itsprocessed value registered in the database, determining or supportinganother device to determine that verification of the file is completed.

In accordance with still another aspect of the present invention, thereis provided a server for providing a notary service for a file,including: a communication part for acquiring or supporting anotherdevice to acquire a notary service request for the file; and a processorfor (I), if the notary service request for the file is acquired,generating or supporting another device to generate a specific messagedigest of the file by using a hash function, and (II), if one ofanchoring conditions is satisfied, registering or supporting anotherdevice to register a representative hash value or its processed value ina database, wherein the representative hash value is generated by usinga specific hash value and its corresponding at least one neighboringhash value, and wherein the specific hash value is a hash value of aresult acquired by encoding the specific message digest with a privatekey of a specific user and a private key of the server.

In accordance with still yet another aspect of the present invention,there is provided a server for verifying a file recorded by using anotary service, including: a communication part for acquiring orsupporting another device to acquire a verification request for thefile; and a processor for, on condition that the server has acquired anotary service request for the file, and then has registered a firstrepresentative hash value or its processed value in a database, whereinthe first representative hash value is generated by using a firstspecific hash value and its corresponding at least one neighboring hashvalue under one of anchoring conditions, and wherein the first specifichash value is a hash value of a result acquired by encoding a specificmessage digest of the file with a private key of a specific user and aprivate key of the server, if a second representative hash value or itsprocessed value, generated by using input data included in theverification request, corresponds to the first representative hash valueor its processed value registered in the database, determining orsupporting another device to determine that verification of the file iscompleted.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings attached below to explain example embodiments of thepresent invention are only part of example embodiments of the presentinvention and other drawings may be obtained based on the drawingswithout inventive work for those skilled in the art:

FIG. 1 is a block diagram illustrating a configuration of a server thatprovides a notary service for a file and verifies the file recorded byusing the notary service, in accordance with one example embodiment ofthe present invention.

FIG. 2 is a sequence diagram illustrating a process of performing thenotary service for the file in response to a request from a single user.

FIGS. 3 and 4 are diagrams illustrating examples of Merkle treesgenerated in accordance with one example embodiment of the presentinvention.

FIG. 5 is a sequence diagram illustrating a process of performing averification service for the file in response to a request from a singleuser.

FIG. 6 is a sequence diagram illustrating a parallel signing process ofperforming in parallel the notary service in response to notary servicerequests from multiple users.

FIG. 7 is a sequence diagram illustrating a serial signing process ofperforming the notary service sequentially in response to notary servicerequests from multiple users.

FIG. 8 is a sequence diagram illustrating a process of performingverification for the file authenticated with signings of the multipleusers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, specificembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention. It is to be understood that the variousembodiments of the present invention, although different, are notnecessarily mutually exclusive. For example, a particular feature,structure, or characteristic described herein in connection with oneembodiment may be implemented within other embodiments without departingfrom the spirit and scope of the present invention. In addition, it isto be understood that the position or arrangement of individual elementswithin each disclosed embodiment may be modified without departing fromthe spirit and scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claims,appropriately interpreted, along with the full range of equivalents towhich the claims are entitled. In the drawings, like numerals refer tothe same or similar functionality throughout the several views.

FIG. 1 is a block diagram illustrating a configuration of a server thatprovides a notary service for a file and verifies the file recorded byusing the notary service, in accordance with one example embodiment ofthe present invention. And FIG. 2 is a sequence diagram illustrating aprocess of performing the notary service for the file in response to arequest from a single user.

Before explaining each of example embodiments, the following aredefinitions of expressions used in the present specification. On theleft of ‘:’ is an expression and on the right is a definition of theexpression.

<Definitions of Expressions>

PrivX: Private key of X

PubX: Public key of X

AESX: AES secret key of X

Enc_(PrivX)(Y): Output of encryption of Y using PrivX

Dec_(PubX)(Y): Output of decryption of Y using PubX

Enc_(AESX)(Y): Output of AES encryption of Y using AESX

Dec_(AESX)(Y): Output of AES decryption of Y using AESX

Hash(Y): Hash value of Y

First of all, a process of performing the notary service for the file inresponse to the request from the single user is explained by referringto FIGS. 1 and 2.

By referring to FIG. 1, the server 100 that performs the notary servicefor the file in accordance with said one example embodiment of thepresent invention may include a communication part 110 and a processor120. The server in each example embodiment may be a separate server, butfor convenience, it is explained that the service is performed by thesingle server 100.

The communication part 110 may be configured to transmit and receivedata to and from the user or a user device, and a database 200. First,the communication part 110 may acquire or support another device toacquire a notary service request for the file at a step of S210. Asillustrated in FIG. 2, if the notary service request for the file isacquired, the file and PubU, which is a public key of the user whorequests the notary service, may be acquired. The communication part 110may respond to the request at a step of S220 where the request and itscorresponding response may be performed during one TCP session.

If the notary service request for the file is acquired, the processor120 may generate or support another device to generate a message digestof the file using a hash function, i.e., MD=Hash(File), at a step ofS215. Herein, the hash function may vary in its type. For example, thehash function may be triple sha256. Also, the hash function in thepresent specification generally means a function to transform theoriginal file, but may include a function that just stores the filewithout any modification in an extreme case. In this case, the messagedigest generated by using the hash function may be the same as the file.

The message digest generated in response to the notary service requestfor the file at the step of S220 may be transmitted to the user whorequests the notary service for the file. If the user requests thenotary service through the user device, not shown in the diagram, thegenerated message digest may be transmitted to the user device.

Next, the communication part 110 may acquire EncPrivU(MD), calculated byencoding the message digest with a private key PrivU of the user, fromthe user at a step of S225. In this case, the message digest and thePubU may also be received from the user because the TCP session may bedisconnected after the response of the step S220. For reference,although the present specification is described by using expressionsEncPriv(MD) and EncPub(MD) of encoding the message digest with a privatekey and a public key, the expressions may be replaced with SigPriv(File)and SigPub(File). Additionally, in case that the message digest isgenerated more than once, expressions SigPriv(MD) and SigPub(MD) may beused.

Further, if the EncPrivU(MD), calculated by encoding the message digestwith the PrivU, is acquired, and if the generated message digest Bcorresponds to information A which is DecPubU(EncPrivU(MD)) acquired bydecoding the EncPrivU(MD) with the PubU at a step of S230-2, theprocessor 120 may generate or support another device to generate a hashvalue of a first encoded message digest generated by encoding themessage digest with the PrivU and a private key PrivC of the server 100at a step of S240, and may register or support another device toregister the generated hash value in the database 200 at a step of S250.The reason for registering the message digest in the form of a hashvalue in the database 200 is that the size of the data needs to bereduced due to the limits on a storage capacity of the database 200.Herein, the database 200 may be a blockchain of virtual currency. Forexample, it may be a bitcoin blockchain.

For reference, in the FIG. 2, the expression ‘DecPubU(EncPrivU(MD))==MD’is used to represent that the A corresponds to the B, but the expressionof the present invention is not limited thereto. For example,‘True==VerPubU(SigPrivU(File))’ may also represent the samerelationship. Additionally, in case that the message digest is generatedmore than once, the expression ‘True VerPubU(SigPrivU(MD))’ may be used.

Moreover, if the A corresponds to the B, the processor 120 may registeror support another device to register Hash[EncPrivC(EncPrivU(MD))] whichis the hash value of the first encoded message digest generated byencoding the message digest in sequence with the PrivU and the PrivC, inthe database 200. In other words, the hash value of the first encodedmessage digest may be registered in the database 200 after the user, whois a client, signs the message digest first with the PrivU and then theserver 100, which is an authentication officer, signs it with the PrivC.However, the order of signing may be different from this. Especially, ifa session between the user and the server 100 is being maintained, theserver 100 may sign first and then the user may.

In case that the hash value of the first encoded message digestgenerated by encoding the message digest with the PrivU and the PrivC isregistered in the database 200, the communication part 110 may acquire atransaction ID, i.e., TxID, from the database 200 at a step of S255,wherein the TxID indicates a location of the hash value of the firstencoded message digest registered in the database 200.

On the other hand, if the A does not correspond to the B at a step of230-1, the processor 120 may send a message of unsuccessful registrationto the user by reason that the user is not a person related to the file,e.g. a transactor, at a step of S235.

Additionally, if the A corresponds to the B, the processor 120 may storeor support another device to store the file at a step of S245. Herein,the file may be encrypted with a symmetric key encryption algorithm suchas AES, i.e., Advanced Encryption Standard. In this case, the secret keymay be a certain secret key processed from the public key of the user,but the scope of the present invention is not limited thereto.

The processor 120 may store or support another device to store the PubU,the message digest MD, the EncPrivU(MD), and the TxID. Moreover, theprocessor 120 may further store or support another device to storeEncPrivC(EncPrivU(MD)), which is the first encoded message digestgenerated by encoding the MD in sequence with the PrivU and the PrivC,and its hash value Hash[EncPrivC(EncPrivU(MD))].

If authentication information is registered in the database 200 asstated above, the communication part 110 may send a message ofsuccessful registration to the user at a step of S260.

However, in case of the aforementioned example embodiment, there aredisadvantages such as a bottleneck in providing the service caused bythe increased number of transaction requests because an OP message isgenerated for every file and recorded in the blockchain, and high costsfor a service management because the transaction fee must be paid everytime.

Hereinafter, an authentication system is explained that can takeadvantage of and further complement the authentication system for thefile to perform the authentication in real-time without a possibility offorgery and falsification, thereby guaranteeing a fast service andreducing the costs while. Such an authentication system uses a distinctdata structure managed by the server 100, unlike the aforementionedexample embodiment.

If the notary service request for the file is acquired through thecommunication part 110, the aforementioned processor 120 may generate orsupport another device to generate a specific message digest of the fileusing the hash function. The repeated explanation is omitted as it issimilar to the aforementioned example embodiment. Herein, the notaryservice for the file may be an authentication service for the file or arevocation service for the file, unlike the aforementioned exampleembodiment.

Also, if one of anchoring conditions is satisfied, the processor 120 mayregister or support another device to register a representative hashvalue or its processed value in a database, wherein the representativehash value is generated by using a specific hash value and itscorresponding at least one neighboring hash value, and wherein thespecific hash value is a hash value of a result acquired by encoding thespecific message digest with a private key of a specific user and theprivate key of the server 100. In other words, the processor 120, ifsaid one of the anchoring conditions is satisfied, may generate orsupport another device to generate the representative hash value or itsprocessed value by calculating the hash value of the result and itscorresponding at least one neighboring hash value, acquired by encodingthe specific message digest with the private key PrivU of the specificuser and the private key PrivC of the server 100, and register orsupport another device to register the generated representative hashvalue or its processed value in the database, instead of registering thehash value of the result of encoding the specific message digest withthe PrivU and the PrivC as stated above at the step of S240. Herein, thedatabase may not be managed by the server 100 like the aforementioneddatabase 200, e.g. the blockchain of the virtual currency, but may alsobe managed by the server 100. The explanation in the presentspecification is focused on the database 200 which is not managed by theserver 100, but the technical idea of the present invention may beapplied to the database managed by the server 100.

The calculation of the specific hash value and its corresponding atleast one neighboring hash value may be performed by various functions.Assuming the specific hash value to be input and the neighboring hashvalues to be x1, x2, . . . , and xn, the representative hash value t maybe expressed as the following equation.

t=hash(function(input, x1, x2, . . . , xn))   <Equation>

Herein, the server 100 may store or support another device to store thespecific hash value and its corresponding at least one neighboring hashvalue in a certain form of a data structure and manage them. In thisregard, the data structure may vary, and one example thereof may be astructure of a Merkle tree. In this case, the calculation of thespecific hash value and its corresponding at least one neighboring hashvalue may be performed by using the Merkle tree.

In other words, the processor 120 may generate or support another deviceto generate at least one Merkle tree including a specific leaf nodewhere the specific hash value is allocated, and if said one of theanchoring conditions is satisfied, may register or support anotherdevice to register the representative hash value or its processed value,which is calculated from the specific hash value and at least one hashvalue allocated to at least one of other leaf nodes which have samedepth as the specific leaf node in the Merkle tree, in the database 200.

More specifically, (x1) the processor 120 may calculate or supportanother device to calculate (i) the specific hash value and (ii) a hashvalue allocated to a sibling node of the specific leaf node where thespecific hash value is allocated, to thereby acquire a resultant value,and then allocate or support another device to allocate a hash value ofthe resultant value to a parent node of the specific leaf node. (x2) Ifthe parent node is a root node of the Merkle tree, the hash value of theresultant value allocated to the parent node may be regarded as therepresentative hash value. (x3) On the other hand, if the parent node isnot the root node of the Merkle tree, the processor 120 may repeat orsupport another device to repeat the steps of (x1) to (x3) by using thehash value allocated to the parent node as the specific hash value.

Additionally, the processor 120 may register or support another deviceto register the hash value ultimately allocated to the root node of theMerkle tree in the database 200 as the representative hash value.Herein, the processed value of the representative hash value may beregistered. For example, a value resulting from hex operation on therepresentative hash value may be registered.

A first data structure and a second data structure may be linked in aform of a chain if the server 100 stores the specific hash value and theat least one neighboring hash value in the first data structure and thenstores and manages the second data structure in an identical form withthe first data structure.

Especially, as stated above, if the first data structure and the seconddata structure are Merkle trees, a root value of the first datastructure or a hash value of the root value may be allocated to a firstleaf node of the second data structure.

Moreover, data integrity may be further ensured by verifying the firstdata structure when the second data structure is generated. Verificationof the second data structure will be explained later.

Further, in case of a first Merkle tree among two or more Merkle treeslinked in a form of a chain, a hash value of certain message data or itsprocessed value comprised of text, number or symbol may be allocated toa first leaf node of the first Merkle tree. For example, a hash value ofa first input message given by the server 100 at the time of generationof the Merkle tree may be allocated.

FIGS. 3 and 4 are diagrams illustrating examples of the Merkle treesgenerated in accordance with said one example embodiment of the presentinvention.

FIG. 3 illustrates a Merkle tree with four (2²) leaf nodes. As theillustrated Merkle tree is the first Merkle tree whose tree_id is zero,the hash value triplesha256digest(coinplug_unique_message) of thecertain message data “Coinplug 2016-01-01” is allocated to a node h0which is the first leaf node. In case that the notary service requestfor the file is acquired, the processor 120 may generate or supportanother device to generate a leaf node next to the last leaf node of thecurrently configured Merkle tree and allocate or support another deviceto allocate the specific hash value or its processed value to thegenerated leaf node. For example, if allocation is completed up to anode h1, which is a second leaf node of the Merkle tree in FIG. 3, at aprevious step, a node h2 which is a next leaf node may be generated andthe specific hash value or its processed valuetriplesha256digest(input2) may be allocated to the node h2. Further, theprocessor 120 may calculate or support another device to calculate (i)the specific hash value and (ii) a hash value allocated to a siblingnode h3 of the node h2, which is a third leaf node where the specifichash value is allocated to, to thereby acquire a resultant value. A hashvalue of the resultant value may be allocated to a parent node h23 ofthe node h2 and the node h3. As the parent node h23 is not the root nodeof the Merkle tree, the processor 110 may repeat or support anotherdevice to repeat the above process by using the hash value allocated tothe node h23 as the specific hash value. In other words, the hash valueallocated to the node h23 and a hash value allocated to a node h01 maybe used to generate a calculated value which is allocated to a nodeh0123, i.e., a parent node of the node h23 and the node h01. Herein, asthe node h0123 is the root node of the Merkle tree, the processor 120may register or support another device to register a processed valuehex(h{node_index}) of the hash value allocated to the node h0123 in thedatabase 200.

Meanwhile, the aforementioned anchoring conditions may include at leastone of (i) acquisition of a certain number of message digests includingthe specific message digest in response to respective notary servicerequests, (ii) a certain time lapse, (iii) generation of a block in ablockchain, and (iv) one or more characteristics of the user whorequests the notary service.

For example, if the message digests are acquired as much as the numberof leaf nodes of the Merkle tree in response to the respective notaryservice requests, a hash value of a result acquired by encoding each ofthe message digests with the private key of each user and the privatekey of the server 100 may be input of the Merkle tree, that is, valuesallocated to the leaf nodes.

Also, the processor 120 may generate or support another device togenerate a root value of the Merkle tree by the certain time as thecondition (ii) above. In this case, if the certain time is elapsed, theprocessor 120 may generate or support another device to generate theMerkle tree using the input of the certain time and may register orsupport another device to register the root value of the Merkle tree inthe database 200.

However, in this case, there may be no value allocated to the siblingnode of the specific leaf node where the specific hash value isallocated despite the certain time lapse. In case that no hash value isallocated to the sibling node of the specific leaf node despite thecertain time lapse, the processor 120 may allocate or support anotherdevice to allocate a certain hash value to the sibling node to therebyproduce the root value of the Merkle tree in the aforementioned way. Forexample, the processor 120 may copy and allocate the specific hash valueto the sibling node.

The characteristics of the user who requests the notary service may beat least part of information on cost paid by the user who requests thenotary service, information on a time-zone during which the notaryservice is performed, information on location where the notary serviceis performed, and information on a type of the user who requests thenotary service. But the scope of the present invention is not limitedthereto.

Meanwhile, if generation of a new Merkle tree starts and if said one ofthe anchoring conditions is satisfied without any notary servicerequest, the processor 120 may generate or support another device togenerate the new Merkle tree with first and second leaf nodes wherecertain message data is respectively allocated, and may register orsupport another device to register a root value or its processed valueof the new Merkle tree in the database 200. In this case, the Merkletree may be generated with two leaf nodes.

However, if the server 100 stores the specific hash value and the atleast one neighboring hash value in the first data structure and thenstores and manages the second data structure in an identical form withthe first data structure as aforementioned, the first data structure andthe second data structure may be linked in a form of a chain.Especially, if the first data structure and the second data structureare the Merkle trees, the root value of the first data structure or ahash value of the root value may be allocated to the first leaf node ofthe second data structure.

FIG. 4 is a diagram illustrating an example of a new Merkle treegenerated as the second data structure in accordance with said oneexample embodiment of the present invention.

By referring to FIG. 4, it is clear that the root value hex(h0123) ofthe Merkle tree whose tree_id is zero in FIG. 3 is allocated to a nodeh4, which is a first leaf of the new Merkle tree, astriplesha256digest(input4). In such a manner, tracking becomes easiereven in the case of data forgery and, therefore the present inventionhas an advantage of improving the data integrity, by linking multipledata structures created when a transaction occurs.

Next, a process for verifying a file in response to a request from asingle user is explained.

Verification in the present specification may be requested by thetransactor or a third party, and may be sorted into a case using thedistinct data structure managed by the server 100 and a case withoutusing the distinct data structure. Both terms of “audit” and“verification” may be used. First of all, the verification performedwithout using the distinct data structure managed by the server 100 isexplained.

The file may be verified by a separate device which may refer toinformation on the aforementioned server 100, or by the aforementionedserver 100. Hereinafter, the explanation is based on the verification ofthe file by the aforementioned server 100 for convenience.

FIG. 5 is a sequence diagram illustrating a process of performing averification service for the file in response to the request from thesingle user.

By referring to FIG. 5, similarly to the aforementioned example, thecommunication part 110 may acquire a verification request for the fileat a step of S510. As illustrated in FIG. 5, if the verification requestfor the file is acquired, the file and the PubU, which is the public keyof the user who requests the verification, may be acquired. Thecommunication part 110 may respond to the request, and the request andits corresponding response may be performed within one TCP session.

As stated above, on condition that the server 100 has determined theuser, who requested the notary service of the file, as related to thefile in response to the notary service request for the file and, as aresult, that the server 100 has stored the hash value of the firstencoded message digest, generated by encoding the message digest of thefile with the PrivU and the PrivC, in the database 200, and has beenmanaging its corresponding transaction ID, if the verification requestfor the file is acquired, the processor 120 may acquire or supportanother device to acquire the transaction ID corresponding to at leastone of the PubU and the message digest of the file. In this case, thetransaction ID, i.e., TxID, may have been stored in the server 100 or ina device which the server 100 may refer to.

In case that the communication part 110 receives the verificationrequest for the file at the step of S510, if the file is acquired forthe verification, the processor 120 may generate or support anotherdevice to generate an original message digest of the file using the hashfunction, i.e., MD=Hash(File), at a step of S515. In this case, theprocessor 120 may refer to the transaction ID corresponding to at leastone of the PubU and the generated original message digest of the file.

If no information corresponding to the original message digest is founddespite the verification request at a step of S520-1, the communicationpart 110 may send a message of unsuccessful verification to the user ata step of S525.

Also, if the information, which is the transaction ID corresponding tothe original message digest, is found at a step of S520-2, thecommunication part 110 may send a query to the database 200 using theTxID at a step of S525 and acquire an OP message including the hashvalue of the first encoded message digest generated by encoding themessage digest with the PrivU and the PrivC from the database 200 at astep of S530.

Further, if a hash value of a second encoded message digest, generatedby encoding the original message digest with the PrivC and the PrivU,corresponds to the hash value of the first encoded message digest in theOP message, then the processor 120 may determine or support anotherdevice to determine the file as verified at a step of S535.

Herein, the second encoded message digest generated by encoding theoriginal message digest with the PrivC and the PrivU may beEncPrivC(EncPrivU(MD)) which is generated by encoding the originalmessage digest in sequence with the PrivU and the PrivC.

However, even in case that the hash value of X, which is the secondencoded message digest, corresponds to the hash value of the firstencoded message digest in the OP message, if a result valueDecPubU(DecPubC(EncPrivC(EncPrivU(MD)))), acquired by decoding the Xwith a public key PubC of the server 100 and the PubU, corresponds tothe message digest of the file, the processor 120 may further determineor support another device to determine the file as verified at a step ofS540. In other words, the verification of the file may be completed withtwo more steps. This is because there may be a possibility of changes inthe private key, the public key, etc. of the user.

The three steps of the verification above may be represented as theexpressions below.

OP_MESSAGE==Hash [Enc _(PrivC)(Enc _(PrivU)(MD))]

Encp _(PrivU)(MD)==Dec _(PubC) [Enc _(PrivC)(Enc _(PrivU)(MD))]

MD (=Hash [File])==Dec _(PubU) [Enc _(PrivU)(MD)]  <Expression 1>

If the verification of the file is successful, the communication part110 may send a message of successful verification to the user at a stepof S545.

Also, if the file is determined as verified, the processor 120 may allowa download of the file. In this case, the user may download the filethrough the user device, etc.

Next, the verification performed by using the distinct data structuremanaged by the server 100 is explained.

First of all, as stated above, on condition that the server 100 hasacquired the notary service request for the file, and then hasregistered the aforementioned representative hash value, referred tohere for convenience as a first representative hash value, or itsprocessed value in the database 200, wherein the first representativehash value is generated by using the aforementioned specific hash value,referred to here for convenience as a first specific hash value, and itscorresponding at least one neighboring hash value under said one of theanchoring conditions, and wherein the first specific hash value is thehash value of the result acquired by encoding the specific messagedigest of the file with the private key of the specific user and theprivate key of the server 100, if a verification request for the file isacquired, and if a second representative hash value or its processedvalue, generated by using input data included in the verificationrequest, corresponds to the first representative hash value or itsprocessed value registered in the database 200, then the processor 120may determine or support another device to determine that theverification of the file is completed.

In this regard, the second representative hash value may be generated bycalculating a second specific hash value and its corresponding at leastone neighboring hash value, wherein the second specific hash value is ahash value of a result acquired by encoding the specific message digestof the file extracted from the input data included in the verificationrequest with the private key of the specific user and the private key ofthe server.

Herein, the input data included in the verification request may have atleast one of (i) the file, (ii) the specific message digest of the file,or (iii) an ID issued during the notary service for the file.

If the input data includes the file, the specific message digest of thefile may be generated by the aforementioned method, and the secondspecific hash value may be generated based thereon. Further, the secondrepresentative hash value may be generated by calculating the secondspecific hash value and its corresponding at least one neighboring hashvalue.

If the input data includes the ID issued during the notary service, thesecond specific hash value may be set to a value allocated to a leafnode corresponding to the ID in the previously generated Merkle tree. Inthe examples illustrated in FIGS. 3 and 4, the ID may be a unique ID.

The same explanation for the first specific hash value aforementionedmay be applied to the second specific hash value. That is, thecalculation of the second specific hash value and its corresponding atleast one neighboring hash value may be performed by various functions.Thus the explanation thereof is omitted by referring to the above.

In this case, the calculation of the second specific hash value and itscorresponding at least one neighboring hash value may be performed byusing a Merkle tree. If the verification request is acquired, theprocessor 120 may identify or support another device to identifyinformation on the Merkle tree related to the input data and on its leafnodes.

Further, the second representative hash value may be calculated by usingthe second specific hash value allocated to a specific leaf node of theMerkle tree, and a hash value allocated to at least one of other leafnodes which have same depth as the specific leaf node in the Merkletree.

In case that the service is performed by using the database not managedby the server 100, e.g. the blockchain of the virtual currency, theprocessor 120 may refer or support another device to refer to a certaintransaction ID corresponding to the information on the identified Merkletree.

In this case, if the verification request for the file is acquired, theprocessor 120 may refer or support another device to refer to thecertain transaction ID, and acquire or support another device to acquirean OP message from the database 200 by referring to the certaintransaction ID. Also, if the second representative hash value or itsprocessed value, generated by using the input data included in theverification request, corresponds to the first representative hash valueor its processed value included in the OP message, the verification ofthe file may be determined as completed.

Meanwhile, the certain transaction ID may be provided as included in theinput data. In other words, in response to the verification request, theuser may transmit or support another device to transmit the certaintransaction ID to the server 100 in addition to at least one of (i) thefile, (ii) the specific message digest of the file, or (iii) the IDissued during the notary service for the file.

In a calculation process of the verification, the processor 120 maygenerate or support another device to generate a new Merkle tree. Inthis process, the Merkle tree generated during the aforementioned notaryservice may be used. In other words, (x1) the processor 120 maycalculate or support another device to calculate (i) the second specifichash value and (ii) a hash value allocated to a sibling node of thespecific leaf node where the second specific hash value is allocated inthe previously generated Merkle tree, to thereby acquire a resultantvalue, and then allocate or support another device to allocate a hashvalue of the resultant value to a parent node of the specific leaf nodein the new Merkle tree. Further, (x2) if the parent node is a root nodeof the new Merkle tree, the processor 120 may compare or support anotherdevice to compare the hash value allocated to the parent node, as thesecond representative hash value, with the first representative hashvalue or its processed value included in the OP message, and (x3) if theparent node is not the root node of the Merkle tree, repeat or supportanother device to repeat the steps of (x1) to (x3) by using the hashvalue allocated to the parent node as the second specific hash value.

The processor 120, if the root value or its processed value ultimatelygenerated in the Merkle tree corresponds to the first representativehash value or its processed value in the OP message, may determine orsupport another device to determine that the verification of the file iscompleted.

In the present invention, if a Merkle tree with n^(m)(=N) leaf nodes isgenerated during the notary service, integrity of the transaction may beconfirmed quickly as the verification of the file is possible bycalculating only as much as the height of the Merkle tree, i.e.,log_(n)N=m.

On the other hand, if the input data is acquired, the processor 120 mayidentify or support another device to identify at least part of theinformation on the Merkle tree related to the input data and on its leafnodes, by referring to time information related to the input data.

Hereinafter, the verification process is explained by taking an exampleillustrated in FIG. 3.

By referring to FIG. 3 again, if verification of input 2 is requested,the processor 120 may identify or support another device to identify theinformation on the previously generated Merkle tree and on its leafnodes by referring to the information on the input data, and acquire orsupport another device to acquire the OP message from the database 200by transmitting the certain transaction ID corresponding to theinformation on the identified Merkle tree whose tree id is zero to thedatabase 200. Then, the processor 120 may generate or support anotherdevice to generate the new Merkle tree by using the input 2. As a hashvalue of the input 2, i.e., triplesha256digest(input2), is allocated tothe node h2, the processor 120 may calculate or support another deviceto calculate the hash value allocated to the node h2 and the hash valueallocated to the sibling node h3 of the node 2 in the previouslygenerated Merkle tree, to thereby acquire a resultant value. A hashvalue of the resultant value may be allocated to the parent node h23 ofthe node h2 and the node h3. As the node h23 is not the root node of thenew Merkle tree, the processor 120 may repeat or support another deviceto repeat the above process by using the hash value allocated to thenode 23 as the second specific hash value. In other words, by using thehash value allocated to the node h23 as the second specific hash value,the hash value allocated to the node h23 and the hash value allocated tothe node h01 in the previously generated Merkle tree may be calculatedand then allocated to the node h0123 which is the parent node of thenode h23 and the node h01. Herein, as the node h0123 is the root node ofthe Merkle tree, the processor 120 may compare or support another deviceto compare the processed value hex(h{node_index}) of the hash valueallocated to the node h0123 with the first representative hash value orits processed value included in the OP message.

Next, a process for performing the notary service of the file inresponse to requests from multiple users is explained in accordance withanother example embodiment of the present invention. However, therepeated explanation is omitted. Further, the same numerals indicate thesame devices in the previous embodiment of the present invention. Firstof all, an authentication system without using the distinct datastructure managed by the server 100 is explained.

FIG. 6 represents a parallel signing process of performing the notaryservices in parallel, and FIG. 7 represents a serial signing process ofperforming the notary services sequentially, in response to the notaryservice requests from at least part of the multiple users.

First of all, by referring to FIG. 6, if at least two notary servicerequests for the file are acquired from at least two of the multipleusers at steps of S610 and S620, the processor 120 may generate orsupport another device to generate the message digest of the file, i.e.,MD=Hash(File), using the hash function at each step of S612 and S622.Moreover, if a first message digest generated by encoding the messagedigest with a private key PrivU1 of a first user and a second messagedigest generated by encoding the message digest with a private keyPrivU2 of a second user are acquired at steps of S640 and S650, and ifeach piece of (i) information A′ which is DecPubU1(EncPrivU1(MD))acquired by decoding the first message digest with a public key PubU1 ofthe first user and (ii) information B′ which is DecPubU2(EncPrivU2(MD))acquired by decoding the second message digest with a public key PubU2of the second user corresponds to the generated message digest C′, whichis the MD, at a step of S640-3, then the processor 120 may register orsupport another device to register a hash value of a third messagedigest, generated by encoding the MD with the PrivU1, the PrivU2, andthe PrivC, in the database 200 at a step of S675.

Next, the communication part 110 may acquire a transaction ID indicatinga location of the registered hash value of the third message digest inthe database 200 at a step of S680.

Moreover, if each of the A′ and the B′ corresponds to the C′, theprocessor 120 may register or support another device to registerEncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which is acquired by encoding adata group with the PrivC, in the database 200, wherein the data groupis comprised of the first message digest generated by encoding the MDwith the PrivU1 and the second message digest generated by encoding theMD with the PrivU2.

Next, by referring to FIG. 7, if the notary service request for the fileis acquired at each step of S710 and S735, the processor 120 maygenerate or support another device to generate the message digest of thefile using the hash function, i.e., MD=Hash(File), at each step S712 andS737. In this case, as illustrated in FIG. 7, the PubU1, the PubU2, andthe file may be acquired together.

If (i) the first message digest EncPrivU1(MD), generated by encoding themessage digest with the PrivU1, is acquired at a step of S720, andinformation A″, which is the DecPubU1(EncPrivU1(MD)) acquired bydecoding the first message digest with the PubU1, corresponds to thegenerated message digest B″, which is the MD, and if (ii)EncPrivU2(EncPrivU1(MD)), generated by encoding the message digest withthe PrivU1 and the PrivU2, is acquired at a step of S745, andinformation C″ which is DecPubU2(EncPrivU2(EncPrivU1(MD))) acquired bydecoding the EncPrivU2(EncPrivU1(MD)) with the PubU2 corresponds toinformation D″ which is the first message digest EncPrivU1(MD) at a stepof S760, then the processor 120 may register or support another deviceto register the hash value of the third message digest, generated byencoding the message digest with the PrivU1, the PrivU2, and the PrivC,in the database 200 at a step of S775.

Moreover, if the A″ corresponds to the B″, and if the C″ corresponds tothe D″, the processor 120 may register or support another device toregister SO=EncPrivC(EncPrivU2(EncPrivU1(MD))), which is generated byencoding the message digest in sequence with the PrivU1, the PrivU2, andthe PrivC, in the database 200.

Herein, the communication part 110 may acquire the transaction ID, i.e.,TxID, indicating a location of the registered hash value of the thirdmessage digest in the database 200 at a step of S780.

Next, said another example embodiment of responding to the notaryservice requests from the multiple users in the authentication systemusing the distinct data structure managed by the server 100 is furtherexplained.

The processor 120, (i) if the notary service request for the file isacquired, may generate or support another device to generate thespecific message digest of the file by using the hash function, and,(ii) if one of the anchoring conditions is satisfied, may register orsupport another device to register a representative hash value or itsprocessed value in the database 200, wherein the representative hashvalue is generated by using the specific hash value and itscorresponding at least one neighboring hash value, and wherein thespecific hash value is a hash value of a result acquired by encoding thespecific message digest with the private key of the first user, theprivate key of the second user, and the private key of the server 100.

Herein, in the parallel signing process, the specific hash value may bea hash value of EncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which is acquiredby encoding a data group with the private key of the server 100, whereinthe data group is comprised of a first encoded message digest generatedby encoding the specific message digest with the private key of thefirst user and a second encoded message digest generated by encoding thespecific message digest with the private key of the second user.

On the other hand, in the serial signing process, the specific hashvalue may be a hash value of EncPrivC(EncPrivU2(EncPrivU1(MD))), whichis acquired by encoding the specific message digest in sequence with theprivate key of the first user, the private key of the second user, andthe private key of the server 100.

Next, a process for verifying the authenticated file in response torequests from multiple users is explained. First of all, verificationperformed without using the distinct data structure managed by theserver 100 is explained by referring to FIG. 8. However, the repeatedexplanation is omitted.

FIG. 8 is a sequence diagram illustrating the process for verifying thefile authenticated with signings of the multiple users.

For reference, steps of S825 to S850 represent a serial signing processfor verifying the file sequentially, and steps of S860 to S885 representa parallel signing process for verifying the file in parallel, inresponse to verification requests from at least part of the multipleusers. Both the serial signing process and the parallel process can beapplied to a service provided by the present invention.

By referring to FIG. 8, as stated above, on condition that the server100 has determined the first user and the second user as related to thefile in response to the notary service requests for the file, and as aresult, that the server 100 has stored the hash value of the thirdmessage digest, generated by encoding the MD of the file with thePrivU1, the PrivU2, and the PrivC, in the database 200, and that theserver 100 has been managing its corresponding transaction ID, i.e.,TxID, if at least one of the verification requests for the file isacquired at a step of S810, the processor 120 may acquire the TxIDcorresponding to at least one of an original message digest of the file,i.e., MD=Hash(File), and the public keys of the users who requests theverification of the file.

Also, the communication part 110 may acquire an OP message, whichincludes the hash value of the third message digest from the database200 by referring to the TxID at each step of S835 and S870.

Further, if a hash value of a fourth message digest generated byencoding the original message digest with the PrivC, the PrivU1, and thePrivU2 correspond to the hash value of the third message digest in theOP message, then the processor 120 may determine or support anotherdevice to determine the file as verified at each step of S840 and S875.

In the parallel signing process, the processor 120 may determine orsupport another device to determine the file as verified according towhether Hash[EncPrivC(EncPrivU1(MD)+EncPrivU2(MD))], which is a hashvalue of a first encoded value acquired by encoding a data group withthe PrivC, corresponds to the hash value of the third message digest inthe OP message, wherein the data group is comprised of a fifth messagedigest generated by encoding the original message digest with the PrivU1and a sixth message digest generated by encoding the original messagedigest with the PrivU2.

However, even in case that the hash valueHash[EncPrivC(EncPrivU1(MD)+EncPrivU2(MD))] of Y, which is the firstencoded value acquired by encoding the data group comprised of the fifthmessage digest and the sixth message digest with the PrivC, correspondsto the hash value of the third message digest, generated by encoding themessage digest with the PrivU1, the PrivU2, and the PrivC, in the OPmessage, if (i) a first decoded value obtained by decoding the fifthmessage digest, which is obtained by decoding the Y with the PubC, withthe PubU1 corresponds to the MD, and if (ii) a second decoded valueobtained by decoding the sixth message digest, which is obtained bydecoding the Y with the PubC, with the PubU2 corresponds to the MD, theprocessor 120 may determine or support another device to determine thefile as verified. In other words, the verification of the file may becompleted with three more steps.

The four steps of the verification above may be represented as theexpressions below.

OP_MESSAGE==Hash[Enc _(PrivC)(Enc _(PrivU1)(MD)+Enc_(PrivU2)(MD))]

Enc _(PrivU1)(MD)+Enc_(PrivU2)(MD)==Dec _(PubC) [Enc _(PrivC)(Enc_(PrivU1)(MD)+Enc _(PrivU2)(MD))]

MD (=Hash[File])==Dec _(PubU1) [Enc _(PrivU1)(MD) ]

MD (=Hash[File])==Dec _(PubU2) [Enc _(PrivU2)(MD)]  <Expression 2>

On the other hand, in the serial signing process, the processor 120 maydetermine or support another device to determine the file as verifiedaccording to whether Hash[EncPrivC(EncPrivU2(EncPrivU1(MD)))], which isthe hash value of a second encoded value acquired by encoding theoriginal message digest in sequence with the PrivU1, the PrivU2, and thePrivC, corresponds to the hash value of the third message digest in theOP message.

However, even in case that the hash valueHash[EncPrivC(EncPrivU2(EncPrivU1(MD)))] of Z, which is the secondencoded value acquired by encoding the original message digest insequence with the PrivU1, the PrivU2, and the PrivC, corresponds to thehash value of the third message digest in the OP message, ifDecPubU1(DecPubU2(DecPubC(EncPrivC(EncPrivU2(EncPrivU1(MD)))))) obtainedby decoding the Z in sequence with the PubC, the PubU2, and the PubU1corresponds to the MD, the processor 120 may determine or supportanother device to determine the file as verified. In other words, theverification of the file may be completed with three more steps.

The four steps of the verification above may be represented as theexpressions below.

OP_MESSAGE==Hash [Enc _(PrivC)(Enc _(PrivU2)(Enc _(PrivU1)(MD)))]

Enc _(PrivU2)(Enc _(PrivU1)(MD))==Dec _(PubC) [Enc _(PrivC)(Enc_(PrivU2)(Enc _(PrivU1)(MD)))]

Enc _(PrivU1)(MD)==Dec _(PubU2) [Enc _(PrivU2)(Enc _(PrivU1)(MD))]

MD (=Hash [File])==Dec_(PubU1) [Enc _(PrivU1)(MD)]  <Expression 3>

Next, said another example embodiment of responding to the verificationrequest in the authentication system using the distinct data structuremanaged by the server 100 is further explained.

On condition that the server 100 has acquired the authentication requestfor the file, and then has registered a first representative hash valueor its processed value in the database, wherein the first representativehash value is generated by using a first specific hash value and itscorresponding at least one neighboring hash value under one of theanchoring conditions, and wherein the first specific hash value is thehash value of the result acquired by encoding the specific messagedigest of the file with the private key of the first user, the privatekey of the second user, and the private key of the server, if theverification request for the file is acquired, if a secondrepresentative hash value or its processed value, generated by using theinput data included in the verification request, corresponds to thefirst representative hash value or its processed value registered in thedatabase, the processor 120 may determine or support another device todetermine that the verification of the file is completed.

Herein, in the parallel signing process, the first specific hash valuemay be the hash value of EncPrivC(EncPrivU1(MD)+EncPrivU2(MD)), which isacquired by encoding a data group with the private key of the server,wherein the data group is comprised of the first encoded message digestgenerated by encoding the specific message digest with the private keyof the first user and the second encoded message digest generated byencoding the specific message digest with the private key of the seconduser.

In the serial signing process, the first specific hash value may be thehash value of EncPrivC(EncPrivU2(EncPrivU1(MD))), which is acquired byencoding the specific message digest in sequence with the private key ofthe first user, the private key of the second user, and the private keyof the server.

The present invention has an effect of guaranteeing fast service speedand reducing a transaction cost when providing a notary service for afile to perform authentication and verification in real-time byrecording authentication information in the blockchain of virtualcurrency.

The present invention has another effect of improving service speed andreducing the transaction cost by configuring a Merkle tree by usinginformation on the notary service and registering only a root value ofthe Merkle tree with the blockchain instead of registering all of theinformation on the notary service with the blockchain.

The present invention has still another effect of providing guaranteedintegrity of a database by performing the verification using the Merkletree generated in response to a verification request for the file.

Meanwhile, the processor 120 may control a data flow among thecommunication part 110 and the other components. That is, the processor120 may control the communication part 110 and other components toperform their unique functions, by controlling the data flow among eachcomponent within the server 100.

The processor 120 may include hardware configuration of MPU (MicroProcessing Unit) or CPU (Central Processing Unit), cache memory, databus, etc. Additionally, OS and software configuration of applicationsthat achieve specific purposes may be further included.

The embodiments of the present invention as explained above can beimplemented in a form of executable program command through a variety ofcomputer means recordable to computer readable media. The computerreadable media may include solely or in combination, program commands,data files, and data structures. The program commands recorded to themedia may be components specially designed for the present invention ormay be usable to a skilled person in a field of computer software.Computer readable record media include magnetic media such as hard disk,floppy disk, and magnetic tape, optical media such as CD-ROM and DVD,magneto-optical media such as floptical disk and hardware devices suchas ROM, RAM, and flash memory specially designed to store and carry outprograms. Program commands include not only a machine language code madeby a compiler but also a high-level code that can be used by aninterpreter etc., which is executed by a computer. The aforementionedhardware devices can work as more than a software module to perform theaction of the present invention and they can do the same in the oppositecase. The hardware devices may be combined with memory such as ROM andRAM to store program commands and include a processor such as CPU or GPUcomposed to execute commands stored in the memory and also include acommunication part for sending and receiving signals with externaldevices.

As seen above, the present invention has been explained by specificmatters such as detailed components, limited embodiments, and drawings.While the invention has been shown and described with respect to thepreferred embodiments, it, however, will be understood by those skilledin the art that various changes and modification may be made withoutdeparting from the spirit and scope of the invention as defined in thefollowing claims.

Accordingly, the thought of the present invention must not be confinedto the explained embodiments, and the following patent claims as well aseverything including variants equal or equivalent to the patent claimspertain to the category of the thought of the present invention.

What is claimed is:
 1. A method for providing a notary service for afile, comprising steps of: (a) a server, if a notary service request forthe file is acquired, generating or supporting another device togenerate a specific message digest of the file by using a hash function;and (b) the server, if one of anchoring conditions is satisfied,registering or supporting another device to register a representativehash value or its processed value in a database, wherein therepresentative hash value is generated by using a specific hash valueand its corresponding at least one neighboring hash value, and whereinthe specific hash value is a hash value of a result acquired by encodingthe specific message digest with a private key of a specific user and aprivate key of the server.
 2. The method of claim 1, wherein theanchoring conditions include at least one of (i) acquisition of acertain number of message digests including the specific message digestin response to respective notary service requests, (ii) a certain timelapse, (iii) generation of a block in a blockchain, and (iv) one or morecharacteristics of a user who requests a notary service.
 3. The methodof claim 1, wherein, at the step of (b), the server performs or supportsanother device to perform (i) a process of generating at least oneMerkle tree including a specific leaf node where the specific hash valueis allocated, and (ii) a process of registering, if said one of theanchoring conditions is satisfied, the representative hash value or itsprocessed value, which is calculated by using the specific hash valueand at least one hash value allocated to at least one of other leafnodes which have same depth as the specific leaf node in the Merkletree, in the database.
 4. The method of claim 3, wherein, if said one ofthe anchoring conditions is satisfied, (x1) the server calculates orsupports another device to calculate (i) the specific hash value and(ii) a hash value allocated to a sibling node of the specific leaf node,to thereby acquire a resultant value, and then allocates or supportsanother device to allocate a hash value of the resultant value to aparent node of the specific leaf node; (x2) the server, if the parentnode is a root node of the Merkle tree, registers or supports anotherdevice to register the hash value allocated to the parent node in thedatabase, as the representative hash value; and (x3) the server, if theparent node is not the root node of the Merkle tree, repeats or supportsanother device to repeat the steps of (x1) to (x3) by using the hashvalue allocated to the parent node as the specific hash value.
 5. Themethod of claim 4, wherein, at the step of (x1), if no hash value isallocated to the sibling node of the specific leaf node even though saidone of the anchoring conditions is satisfied, the server allocates orsupports another device to allocate a certain hash value to the siblingnode, and then performs or supports another device to perform the stepsof (x1) to (x3).
 6. The method of claim 1, wherein, if no notary servicerequest is acquired at the step of (a), and if said one of the anchoringconditions is satisfied at the step of (b), the server performs orsupports another device to perform a process of generating a Merkle treewith first and second leaf nodes where certain message data isrespectively allocated, and a process of registering a root value or itsprocessed value of the Merkle tree in the database.
 7. The method ofclaim 1, wherein the notary service for the file includes at least oneof an authentication service for the file and a revocation service forthe file.
 8. The method of claim 1, wherein the database is a blockchainof a virtual currency or the database is managed by the server.
 9. Amethod for verifying a file recorded by using a notary service,comprising steps of: (a) a server acquiring or supporting another deviceto acquire a verification request for the file, on condition that theserver has acquired a notary service request for the file, and then hasregistered a first representative hash value or its processed value in adatabase, wherein the first representative hash value is generated byusing a first specific hash value and its corresponding at least oneneighboring hash value under one of anchoring conditions, and whereinthe first specific hash value is a hash value of a result acquired byencoding a specific message digest of the file with a private key of aspecific user and a private key of the server; and (b) the server, if asecond representative hash value or its processed value, generated byusing input data included in the verification request, corresponds tothe first representative hash value or its processed value registered inthe database, determining or supporting another device to determine thatverification of the file is completed.
 10. The method of claim 9,wherein the step of (a) includes: (a1) the server, if the verificationrequest is acquired, referring or supporting another device to refer toa certain transaction ID related to the file; and (a2) the serveracquiring or supporting another device to acquire an OP message from thedatabase by referring to the certain transaction ID, and wherein, at thestep of (b), if the second representative hash value or its processedvalue generated by using the input data included in the verificationrequest corresponds to the first representative hash value or itsprocessed value included in the OP message, the server determines orsupports another device to determine that the verification is completed.11. The method of claim 10, wherein, at the step of (al), if theverification request is acquired, the server performs or supportsanother device to perform a process of identifying information on aMerkle tree related to the input data and on its leaf nodes, and aprocess of referring to the certain transaction ID which corresponds tothe information on the identified Merkle tree.
 12. The method of claim9, wherein the second representative hash value is generated by using asecond specific hash value and its corresponding at least oneneighboring hash value, and wherein the second specific hash value is ahash value of a result acquired by encoding the specific message digestof the file extracted from the input data included in the verificationrequest with the private key of the specific user and the private key ofthe server.
 13. The method of claim 12, wherein the secondrepresentative hash value is calculated by using the second specifichash value allocated to a specific leaf node of a Merkle tree, and ahash value allocated to at least one of other leaf nodes which have samedepth as the specific leaf node in the Merkle tree.
 14. The method ofclaim 13, wherein (x1) the server calculates or supports another deviceto calculate (i) the second specific hash value and (ii) a hash valueallocated to a sibling node of the specific leaf node where the secondspecific hash value is allocated, to thereby acquire a resultant value,and then allocates or supports another device to allocate a hash valueof the resultant value to a parent node of the specific leaf node; (x2)the server, if the parent node is a root node of the Merkle tree,compares or supports another device to compare the hash value allocatedto the parent node, as the second representative hash value, with thefirst representative hash value or its processed value included in an OPmessage retrieved from the database; and (x3) the server, if the parentnode is not the root node of the Merkle tree, repeats or supportsanother device to repeat the steps of (x1) to (x3) by using the hashvalue allocated to the parent node as the second specific hash value.15. The method of claim 9, wherein the database is a blockchain of avirtual currency or the database is managed by the server.
 16. A serverfor providing a notary service for a file, comprising: a communicationpart for acquiring or supporting another device to acquire a notaryservice request for the file; and a processor for (I), if the notaryservice request for the file is acquired, generating or supportinganother device to generate a specific message digest of the file byusing a hash function, and (II), if one of anchoring conditions issatisfied, registering or supporting another device to register arepresentative hash value or its processed value in a database, whereinthe representative hash value is generated by using a specific hashvalue and its corresponding at least one neighboring hash value, andwherein the specific hash value is a hash value of a result acquired byencoding the specific message digest with a private key of a specificuser and a private key of the server.
 17. The server of claim 16,wherein the anchoring conditions include at least one of (i) acquisitionof a certain number of message digests including the specific messagedigest in response to respective notary service requests, (ii) a certaintime lapse, (iii) generation of a block in a blockchain, and (iv) one ormore characteristics of a user who requests a notary service.
 18. Theserver of claim 16, wherein the processor performs or supports anotherdevice to perform (i) a process of generating at least one Merkle treeincluding a specific leaf node where the specific hash value isallocated, and (ii) a process of registering, if said one of theanchoring conditions is satisfied, the representative hash value or itsprocessed value, which is calculated by using the specific hash valueand at least one hash value allocated to at least one of other leafnodes which have same depth as the specific leaf node in the Merkletree, in the database.
 19. The server of claim 18, wherein, if said oneof the anchoring conditions is satisfied, (x1) the processor calculatesor supports another device to calculate (i) the specific hash value and(ii) a hash value allocated to a sibling node of the specific leaf node,to thereby acquire a resultant value, and then allocates or supportsanother device to allocate a hash value of the resultant value to aparent node of the specific leaf node; (x2) the processor, if the parentnode is a root node of the Merkle tree, registers or supports anotherdevice to register the hash value of the resultant value allocated tothe parent node in the database, as the representative hash value; and(x3) the processor, if the parent node is not the root node of theMerkle tree, repeats or supports another device to repeat the processesof (x1) to (x3) by using the hash value allocated to the parent node asthe specific hash value.
 20. The server of claim 19, wherein, at theprocess of (x1), if no hash value is allocated to the sibling node ofthe specific leaf node even though said one of the anchoring conditionsis satisfied, the processor allocates or supports another device toallocate a certain hash value to the sibling node, and then performs orsupports another device to perform the processes of (x1) to (x3). 21.The server of claim 16, wherein, if no notary service request isacquired at the process of (I), and if said one of the anchoringconditions is satisfied at the process of (II), the processor performsor supports another device to perform a process of generating a Merkletree with first and second leaf nodes where certain message data isrespectively allocated, and a process of registering a root value or itsprocessed value of the Merkle tree in the database.
 22. The server ofclaim 16, wherein the notary service for the file includes at least oneof an authentication service for the file and a revocation service forthe file.
 23. The server of claim 1, wherein the database is ablockchain of a virtual currency or the database is managed by theserver.
 24. A server for verifying a file recorded by using a notaryservice, comprising: a communication part for acquiring or supportinganother device to acquire a verification request for the file; and aprocessor for, on condition that the server has acquired a notaryservice request for the file, and then has registered a firstrepresentative hash value or its processed value in a database, whereinthe first representative hash value is generated by using a firstspecific hash value and its corresponding at least one neighboring hashvalue under one of anchoring conditions, and wherein the first specifichash value is a hash value of a result acquired by encoding a specificmessage digest of the file with a private key of a specific user and aprivate key of the server, if a second representative hash value or itsprocessed value, generated by using input data included in theverification request, corresponds to the first representative hash valueor its processed value registered in the database, determining orsupporting another device to determine that verification of the file iscompleted.
 25. The server of claim 24, wherein the processor, if theverification request is acquired, refers or supports another device torefer to a certain transaction ID related to the file, and acquires orsupports another device to acquire an OP message from the database byreferring to the certain transaction ID, and, if the secondrepresentative hash value or its processed value generated by using theinput data included in the verification request corresponds to the firstrepresentative hash value or its processed value included in the OPmessage, determines or supports another device to determine that theverification is completed.
 26. The server of claim 25, wherein, if theverification request is acquired, the processor performs or supportsanother device to perform a process of identifying information on aMerkle tree related to the input data and on its leaf nodes, and aprocess of referring to the certain transaction ID which corresponds tothe information on the identified Merkle tree.
 27. The server of claim24, wherein the second representative hash value is generated by using asecond specific hash value and its corresponding at least oneneighboring hash value, and wherein the second specific hash value is ahash value of a result acquired by encoding the specific message digestof the file extracted from the input data included in the verificationrequest with the private key of the specific user and the private key ofthe server.
 28. The server of claim 27, wherein the secondrepresentative hash value is calculated by using the second specifichash value allocated to a specific leaf node of a Merkle tree, and ahash value allocated to at least one of other leaf nodes which have samedepth as the specific leaf node in the Merkle tree.
 29. The server ofclaim 28, wherein (x1) the processor calculates or supports anotherdevice to calculate (i) the second specific hash value and (ii) a hashvalue allocated to a sibling node of the specific leaf node where thesecond specific hash value is allocated, to thereby acquire a resultantvalue, and then allocates or supports another device to allocate a hashvalue of the resultant value to a parent node of the specific leaf node;(x2) the processor, if the parent node is a root node of the Merkletree, compares or supports another device to compare the hash value orits processed value allocated to the parent node, as the secondrepresentative hash value, with the first representative hash value orits processed value included in an OP message retrieved from thedatabase; and (x3) the processor, if the parent node is not the rootnode of the Merkle tree, repeats or supports another device to repeatthe processes of (x1) to (x3) by using the hash value or its processedvalue allocated to the parent node as the second specific hash.
 30. Theserver of claim 24, wherein the database is a blockchain of a virtualcurrency or the database is managed by the server.